Finally, qPCR validation of five upregulated genes (FZD2, EXT1, DCHS1, BMP4, and ALDH1A2) in HF blood samples confirmed that the expression trends of FZD2, DCHS1, BMP4, and ALDH1A2 were consistent with those observed in the GEO database. Here, ALDH1A2 is linked to hydrops fetalis.